/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
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package org.apache.commons.math4.legacy.ode.nonstiff;


import org.apache.commons.math4.legacy.exception.DimensionMismatchException;
import org.apache.commons.math4.legacy.exception.MaxCountExceededException;
import org.apache.commons.math4.legacy.exception.NoBracketingException;
import org.apache.commons.math4.legacy.exception.NumberIsTooSmallException;
import org.apache.commons.math4.legacy.exception.TooManyEvaluationsException;
import org.apache.commons.math4.legacy.ode.FirstOrderDifferentialEquations;
import org.apache.commons.math4.legacy.ode.FirstOrderIntegrator;
import org.apache.commons.math4.legacy.ode.TestProblem1;
import org.apache.commons.math4.legacy.ode.TestProblem3;
import org.apache.commons.math4.legacy.ode.TestProblem4;
import org.apache.commons.math4.legacy.ode.TestProblem5;
import org.apache.commons.math4.legacy.ode.TestProblemHandler;
import org.apache.commons.math4.legacy.ode.events.EventHandler;
import org.apache.commons.math4.legacy.core.jdkmath.AccurateMath;
import org.junit.Assert;
import org.junit.Test;

public class HighamHall54IntegratorTest {

  @Test
  public void testWrongDerivative()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {
      HighamHall54Integrator integrator =
          new HighamHall54Integrator(0.0, 1.0, 1.0e-10, 1.0e-10);
      FirstOrderDifferentialEquations equations =
          new FirstOrderDifferentialEquations() {
            @Override
            public void computeDerivatives(double t, double[] y, double[] dot) {
            if (t < -0.5) {
                throw new LocalException();
            } else {
                throw new RuntimeException("oops");
           }
          }
          @Override
        public int getDimension() {
              return 1;
          }
      };

      try  {
        integrator.integrate(equations, -1.0, new double[1], 0.0, new double[1]);
        Assert.fail("an exception should have been thrown");
      } catch(LocalException de) {
        // expected behavior
      }

      try  {
        integrator.integrate(equations, 0.0, new double[1], 1.0, new double[1]);
        Assert.fail("an exception should have been thrown");
      } catch(RuntimeException de) {
        // expected behavior
      }

  }

  @Test(expected=NumberIsTooSmallException.class)
  public void testMinStep()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

      TestProblem1 pb = new TestProblem1();
      double minStep = 0.1 * (pb.getFinalTime() - pb.getInitialTime());
      double maxStep = pb.getFinalTime() - pb.getInitialTime();
      double[] vecAbsoluteTolerance = { 1.0e-15, 1.0e-16 };
      double[] vecRelativeTolerance = { 1.0e-15, 1.0e-16 };

      FirstOrderIntegrator integ = new HighamHall54Integrator(minStep, maxStep,
                                                              vecAbsoluteTolerance,
                                                              vecRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);
      Assert.fail("an exception should have been thrown");

  }

  @Test
  public void testIncreasingTolerance()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    int previousCalls = Integer.MAX_VALUE;
    for (int i = -12; i < -2; ++i) {
      TestProblem1 pb = new TestProblem1();
      double minStep = 0;
      double maxStep = pb.getFinalTime() - pb.getInitialTime();
      double scalAbsoluteTolerance = AccurateMath.pow(10.0, i);
      double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

      FirstOrderIntegrator integ = new HighamHall54Integrator(minStep, maxStep,
                                                              scalAbsoluteTolerance,
                                                              scalRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);

      // the 1.3 factor is only valid for this test
      // and has been obtained from trial and error
      // there is no general relation between local and global errors
      Assert.assertTrue(handler.getMaximalValueError() < (1.3 * scalAbsoluteTolerance));
      Assert.assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

      int calls = pb.getCalls();
      Assert.assertEquals(integ.getEvaluations(), calls);
      Assert.assertTrue(calls <= previousCalls);
      previousCalls = calls;

    }

  }

  @Test
  public void testBackward()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

      TestProblem5 pb = new TestProblem5();
      double minStep = 0;
      double maxStep = pb.getFinalTime() - pb.getInitialTime();
      double scalAbsoluteTolerance = 1.0e-8;
      double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

      FirstOrderIntegrator integ = new HighamHall54Integrator(minStep, maxStep,
                                                              scalAbsoluteTolerance,
                                                              scalRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);

      Assert.assertTrue(handler.getLastError() < 5.0e-7);
      Assert.assertTrue(handler.getMaximalValueError() < 5.0e-7);
      Assert.assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
      Assert.assertEquals("Higham-Hall 5(4)", integ.getName());
  }

  @Test
  public void testEvents()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    TestProblem4 pb = new TestProblem4();
    double minStep = 0;
    double maxStep = pb.getFinalTime() - pb.getInitialTime();
    double scalAbsoluteTolerance = 1.0e-8;
    double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

    FirstOrderIntegrator integ = new HighamHall54Integrator(minStep, maxStep,
                                                            scalAbsoluteTolerance,
                                                            scalRelativeTolerance);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.addStepHandler(handler);
    EventHandler[] functions = pb.getEventsHandlers();
    double convergence = 1.0e-8 * maxStep;
    for (int l = 0; l < functions.length; ++l) {
      integ.addEventHandler(functions[l],
                                 Double.POSITIVE_INFINITY, convergence, 1000);
    }
    Assert.assertEquals(functions.length, integ.getEventHandlers().size());
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);

    Assert.assertTrue(handler.getMaximalValueError() < 1.0e-7);
    Assert.assertEquals(0, handler.getMaximalTimeError(), convergence);
    Assert.assertEquals(12.0, handler.getLastTime(), convergence);
    integ.clearEventHandlers();
    Assert.assertEquals(0, integ.getEventHandlers().size());

  }

  @Test(expected=LocalException.class)
  public void testEventsErrors()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

      final TestProblem1 pb = new TestProblem1();
      double minStep = 0;
      double maxStep = pb.getFinalTime() - pb.getInitialTime();
      double scalAbsoluteTolerance = 1.0e-8;
      double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

      FirstOrderIntegrator integ =
          new HighamHall54Integrator(minStep, maxStep,
                                     scalAbsoluteTolerance, scalRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);

      integ.addEventHandler(new EventHandler() {
        @Override
        public void init(double t0, double[] y0, double t) {
        }
        @Override
        public Action eventOccurred(double t, double[] y, boolean increasing) {
          return Action.CONTINUE;
        }
        @Override
        public double g(double t, double[] y) {
          double middle = (pb.getInitialTime() + pb.getFinalTime()) / 2;
          double offset = t - middle;
          if (offset > 0) {
            throw new LocalException();
          }
          return offset;
        }
        @Override
        public void resetState(double t, double[] y) {
        }
      }, Double.POSITIVE_INFINITY, 1.0e-8 * maxStep, 1000);

      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);

  }

  private static class LocalException extends RuntimeException {
    private static final long serialVersionUID = 3041292643919807960L;
  }

  @Test
  public void testEventsNoConvergence()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    final TestProblem1 pb = new TestProblem1();
    double minStep = 0;
    double maxStep = pb.getFinalTime() - pb.getInitialTime();
    double scalAbsoluteTolerance = 1.0e-8;
    double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

    FirstOrderIntegrator integ =
        new HighamHall54Integrator(minStep, maxStep,
                                   scalAbsoluteTolerance, scalRelativeTolerance);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.addStepHandler(handler);

    integ.addEventHandler(new EventHandler() {
      @Override
    public void init(double t0, double[] y0, double t) {
      }
      @Override
    public Action eventOccurred(double t, double[] y, boolean increasing) {
        return Action.CONTINUE;
      }
      @Override
    public double g(double t, double[] y) {
        double middle = (pb.getInitialTime() + pb.getFinalTime()) / 2;
        double offset = t - middle;
        return (offset > 0) ? (offset + 0.5) : (offset - 0.5);
      }
      @Override
    public void resetState(double t, double[] y) {
      }
    }, Double.POSITIVE_INFINITY, 1.0e-8 * maxStep, 3);

    try {
      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);
      Assert.fail("an exception should have been thrown");
    } catch (TooManyEvaluationsException tmee) {
        // Expected.
    }

}

  @Test
  public void testSanityChecks()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {
      final TestProblem3 pb  = new TestProblem3(0.9);
      double minStep = 0;
      double maxStep = pb.getFinalTime() - pb.getInitialTime();

      try {
        FirstOrderIntegrator integ =
            new HighamHall54Integrator(minStep, maxStep, new double[4], new double[4]);
        integ.integrate(pb, pb.getInitialTime(), new double[6],
                        pb.getFinalTime(), new double[pb.getDimension()]);
        Assert.fail("an exception should have been thrown");
      } catch (DimensionMismatchException ie) {
        // expected behavior
      }

      try {
        FirstOrderIntegrator integ =
            new HighamHall54Integrator(minStep, maxStep, new double[4], new double[4]);
        integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                        pb.getFinalTime(), new double[6]);
        Assert.fail("an exception should have been thrown");
      } catch (DimensionMismatchException ie) {
        // expected behavior
      }

      try {
        FirstOrderIntegrator integ =
            new HighamHall54Integrator(minStep, maxStep, new double[2], new double[4]);
        integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                        pb.getFinalTime(), new double[pb.getDimension()]);
        Assert.fail("an exception should have been thrown");
      } catch (DimensionMismatchException ie) {
        // expected behavior
      }

      try {
        FirstOrderIntegrator integ =
            new HighamHall54Integrator(minStep, maxStep, new double[4], new double[2]);
        integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                        pb.getFinalTime(), new double[pb.getDimension()]);
        Assert.fail("an exception should have been thrown");
      } catch (DimensionMismatchException ie) {
        // expected behavior
      }

      try {
        FirstOrderIntegrator integ =
            new HighamHall54Integrator(minStep, maxStep, new double[4], new double[4]);
        integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                        pb.getInitialTime(), new double[pb.getDimension()]);
        Assert.fail("an exception should have been thrown");
      } catch (NumberIsTooSmallException ie) {
        // expected behavior
      }

  }

  @Test
  public void testKepler()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    final TestProblem3 pb  = new TestProblem3(0.9);
    double minStep = 0;
    double maxStep = pb.getFinalTime() - pb.getInitialTime();
    double[] vecAbsoluteTolerance = { 1.0e-8, 1.0e-8, 1.0e-10, 1.0e-10 };
    double[] vecRelativeTolerance = { 1.0e-10, 1.0e-10, 1.0e-8, 1.0e-8 };

    FirstOrderIntegrator integ = new HighamHall54Integrator(minStep, maxStep,
                                                            vecAbsoluteTolerance,
                                                            vecRelativeTolerance);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.addStepHandler(handler);
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);
    Assert.assertEquals(0.0, handler.getMaximalValueError(), 1.5e-4);
    Assert.assertEquals("Higham-Hall 5(4)", integ.getName());
  }

}